Linear Polarizer

I shot will it on my recent trip to North Carolina. I had questioned earlier

that I was concerned using this polarizer on my D50 and not purchasing a

circular one. I was told that it would not autofocus or would over-expose image.

So far, just running thru my images, I can see no problems with focusing or

overexpose. Why is this, or is the circular polarizer just another filter they

are trying to get us to buy? The linear one I used was a Hoya 67mm. Any comments?

Sometimes you get lucky.

 

In the simplest of terms, if the orientation of the linear polarizer is not in line with the 'beam splitter' elements of the AF or metering system, you may see no ill effects.

 

I have a vague recollection of a discussion of precession or 'tail chasing' in an AF system where the more the AF tried to find a solution, the more the linear polarizer interfered. This may have involved a rotating front element as well.

Auto exposure and auto focus optics incorporate semi-reflective, non-metallic surfaces which polarize light. If you use a linear polarizer, it has a disproportionate effect on these automated functions, depending on the subject and orientation of the polarizer. A circular polarizer "scrambles" the polarization with a quarter-wave element so that reflections inside the camera are not affected.

 

In short, you got lucky.

In theory it's a bad idea, but in practice the difference is often small. Theory and practice are the same in theory, but not in practice.

It is uncertain if you can use a PL on DSLR. For 100% compability, make sure to use CPL.